The present trend in the solid propellant industry is toward the use of carboxyl containing polymers, e.g. carboxyl modified butadiene polymers, in cure in place binder systems. Studies have shown that in order to make major improvements in the mechanical properties of propellants based on low molecular weight carboxyl modified polymers, it is necessary to use polymers with functional groups in a known position, preferably in a terminal position, rather than randomly distributed along the polymer chain. Accordingly, the carboxyl terminated polybutadiene (CTPB) prepolymer is desirable for use in solid propellants. However, no completely satisfactory curing agent has been found in CTPB. Epoxy resins cure the carboxyl bearing polymers in the absence of certain oxidizers but when acid salts such as MNO.sub.3, MClO.sub.4 or MClO.sub.3 where M is a metal or metal-like cation are added, a poor cure results. Since these oxidizers are normally included in a solid propellant, a curing agent which achieves a good cure in their presence is needed. Propellant grains prepared from a CTPB polymer cured with a trifunctional aziridine, such as tris[1-(2-methyl)aziridinyl] phosphine oxide (MAPO), exhibit desirable processability, strength and flexibility properties. However, such aziridine cured CTPB propellants do not meet stability requirements due to their susceptibility to cure reversion.
We have discovered that the use of a glycidyl thioether as curing agent for CTPB provides a composition which cures to a tough coherent grain in the presence of an inorganic acid salt as oxidizer without significant cure reversion.